Condorcet votes can now properly handle votes expressing equivalency

[rubyvote] / lib / rubyvote / condorcet.rb

diff --git a/lib/rubyvote/condorcet.rb b/lib/rubyvote/condorcet.rb
index 96a103bd479c5bcf3e7d575cacd5d71f4afe8f78..65c664dd28a57417aa0a90395562289c8de0eed4 100644 (file)
--- a/lib/rubyvote/condorcet.rb
+++ b/lib/rubyvote/condorcet.rb
@@ -33,6 +33,8 @@
 
 class CondorcetVote < ElectionVote
 
+  attr_accessor :results
+
   def initialize(votes=nil)
     unless defined?(@candidates)
       @candidates = Array.new
@@ -44,59 +46,80 @@ class CondorcetVote < ElectionVote
       end
     end
     super(votes)
+    @results = Array.new
   end
 
   def tally_vote(vote=nil)
 
-    vote.each_with_index do |winner, index|
+    vote.each_with_index do |winners, index|
       if vote.flatten.length < @candidates.length
-        implied_losers = @candidates.select { |c| not vote.include?(c) }
+        implied_losers = @candidates.select { |c| not vote.flatten.include?(c) }
         vote.push(implied_losers)
       end
       if vote.length - 1 == index
         losers = []
       else
-        losers = vote.last( vote.flatten.length - index )
+        losers = vote.flatten.last( vote.flatten.length - index - 1)
       end
 
       losers.each do |place|
         place = [place] unless place.class == Array
         place.each do |loser|
           
-          next if winner == loser
-
-          @votes[winner] = Hash.new unless @votes.has_key?(winner)
-          @votes[loser] = Hash.new unless @votes.has_key?(loser)
+          winners = [winners] unless winners.class == Array
+          next if winners.include?(loser)
+          winners.each do |winner|
+            @votes[winner] = Hash.new unless @votes.has_key?(winner)
+            @votes[loser] = Hash.new unless @votes.has_key?(loser)
+
+            if @votes[winner].has_key?(loser)
+              @votes[winner][loser] += 1
+            else
+              @votes[winner][loser] = 1
+            end
 
-          if @votes[winner].has_key?(loser)
-            @votes[winner][loser] += 1
-          else
-            @votes[winner][loser] = 1
+            # make sure we have a comparable object
+            @votes[loser][winner] = 0 unless @votes[loser].has_key?( winner )
           end
-
-          # make sure we have a comparable object
-          @votes[loser][winner] = 0 unless @votes[loser].has_key?( winner )
         end
       end
     end
   end
 
-  def result
-    top_result = resultFactory( self )
-    until @candidates.empty?
-      aResult = resultFactory( self )
-      top_result.full_results << aResult
-      filter_out(aResult)
+  def results
+    if @results.size < 2 && (not @candidates.empty?)
+      tabulate
     end
-    top_result
+    @results
+  end
+
+  def result
+    find_only_winner unless @winner
+    @winner
   end
 
   protected
+
   def verify_vote(vote=nil)
     vote.instance_of?( Array ) and
       vote == vote.uniq
   end
 
+  def tabulate
+    find_only_winner unless @winner
+    until @candidates.empty? 
+      aResult = resultFactory( self )
+      @results << aResult.winners
+      filter_out(aResult)
+    end
+  end
+
+  def find_only_winner
+    @winner = resultFactory( self )
+    @results << @winner.winners
+    filter_out(@winner)
+  end
+
 end
 
 class PureCondorcetVote < CondorcetVote
@@ -109,6 +132,7 @@ class CloneproofSSDVote < CondorcetVote
   def resultFactory(init)
     CloneproofSSDResult.new(init)
   end
+
 end
 
 
@@ -128,11 +152,13 @@ class CondorcetResult < ElectionResult
   end
 
   protected
+
   def defeats(candidates=nil, votes=nil)
     candidates = @election.candidates unless candidates
     votes = @election.votes unless votes
 
     defeats = Array.new
+    candidates = [candidates] unless candidates.class == Array
     candidates.each do |candidate|
       candidates.each do |challenger|
         next if candidate == challenger
@@ -154,6 +180,7 @@ class PureCondorcetResult < CondorcetResult
   end
 
   protected
+
   def condorcet
     votes = @election.votes
     candidates = @election.candidates
@@ -168,11 +195,18 @@ class PureCondorcetResult < CondorcetResult
       victors[winner] << loser
     end
 
-    winners = @election.candidates.find_all do |candidate|
-        victors[candidate].length == @election.candidates.length - 1
+    victory_margin = 1
+    while true
+      winners = @election.candidates.find_all do |candidate|
+        victors[candidate].length == @election.candidates.length - victory_margin
+      end
+      if winners.length > 0
+        @winners = winners
+        return @winners
+      else
+        victory_margin += 1
+      end
     end
-
-    @winners << winners if winners.length == 1
   end
 end
 
@@ -183,6 +217,7 @@ class CloneproofSSDResult < CondorcetResult
   end
 
   protected
+
   def cpssd
     votes = @election.votes
     candidates = *@election.candidates
@@ -203,15 +238,22 @@ class CloneproofSSDResult < CondorcetResult
 
       # see the array with the standard defeats
       transitive_defeats = self.defeats(candidates, votes)
+      defeats_hash = Hash.new
+      transitive_defeats.each { |td| defeats_hash[td] = 1 }
 
+      candidates = [candidates] unless candidates.class == Array
       candidates.each do |cand1|
         candidates.each do |cand2|
-          candidates.each do |cand3|
-            if transitive_defeats.include?( [ cand2, cand1 ] ) and
-                transitive_defeats.include?( [ cand1, cand3 ] ) and
-                not transitive_defeats.include?( [ cand2, cand3 ] ) and
-                not cand2 == cand3
-              transitive_defeats << [ cand2, cand3 ]
+          unless cand1 == cand2
+            candidates.each do |cand3|
+              if not cand2 == cand3 and 
+                  not cand1 == cand3 and 
+                  defeats_hash[[cand2, cand1]] and
+                  defeats_hash[[cand1, cand3]] and
+                  not defeats_hash[[cand2, cand3]] 
+                transitive_defeats << [cand2, cand3]
+                defeats_hash[[cand2, cand3]] = 1
+              end
             end
           end
         end